Space vector modulation (SVM) is an algorithm for the control of pulse width modulation (PWM). It is used for the creation of alternating current (AC) waveforms; most commonly to drive three-phase AC powered motors at varying speeds from DC. There are numerous variations of SVM that result in different quality and computational requirements.
A three phase inverter 100 as shown in FIG. 1 must be controlled so that at no time are both switches in the same leg turned on or else the DC supply would be shorted. This requirement may be met by the complementary operation of the switches within a leg. That is, if A+ is on, then A− is off, and vice versa. This leads to eight possible switching vectors for the inverter 100, V0 through V7 with six active switching vectors and two zero vectors, as illustrated in the chart 110 of FIG. 2.
To implement space vector modulation a reference signal Vref is sampled with a frequency fs (Ts=1/fs). The reference signal may be generated from three separate phase references using the αβγ transform, for example. The reference vector is then synthesized using a combination of the two adjacent active switching vectors and one or both of the zero vectors. Various strategies of selecting the order of the vectors and which zero vector(s) to use exist. Strategic selection of the vectors will affect the harmonic content and the switching losses.